Chapter 04 - Sensation and Perception

Grant Clay

Period 3

9/14/08

 

AP Psychology Outline

Chapter 4: Sensation and Perception

 

Red – Definition

Blue - Important Points

Green - Important People & Contributions

 

1. Sensation – The Stimulation of Sense Organs.
2. Perception – the Selection, Organization, and interpretation of Sensory Input.
3. Psychophysics: Basic Concepts & Issues
   
   1. Psychophysics - Study of how physical stimuli are translated into Psychological Experience.
   2. Gustav Fechner

                                                               i.      Psychophysics Psychologists in 1860’s at University of Leipzig.

                                                              ii.      Wilhelm Wundt based lots of research upon Fechner.

                                                            iii.      Question: For any Given Sense, what is the weakest detectable Stimulus?

                                                            iv.      Absolute Threshold – Minimum Stimulus Intensity that an Organism can detect.

                                                             v.      As Stimulus Intensity Increases, the Subject’s probability to responding to Stimuli Gradually increases.

                                                            vi.      The Absolute Threshold is the Stimulus Intensity detected 50% of the time.

                                                          vii.      Just Noticeable Difference (JND) – The smallest difference in stimulus intensity that a specific sense can detect.

                                                         viii.      Weber’s Law – The size of a Just Noticeable Difference is a constant proportion of the size of the initial Stimulus.

1.        Weber’s Fraction – The Fractions that apply to different Sensory Inputs until a Difference is noted. Increases constantly proportionately.

3. Signal-Detection Theory – The detection of stimuli involves Decision Processes, along as Sensory Processes, which are both influenced by a variety of factors besides Stimulus Intensity.

                                                               i.      Noise – Background distractions that lower the chance of detection of a Stimulus.

4. Subliminal Perception – The registration of Sensory Input without conscious awareness.

                                                               i.      Such as Subliminal Messages in movies, advertisements, etc.

John Krosnick – Experimented and found that “Subliminal stimulation generally produces weak effects.

5. Sensory Adaptation – The Gradual Decline in Sensitivity to prolonged Stimulation.

                                                               i.      Ex. You jump in Cold Water; it is very cold at first, But You Get Used to It.

                                                              ii.      Process that keeps people tuned into the changes rather than constants in Sensory Input.

4. Sight
   
   1. The Stimulus: Light

                                                               i.      People need Light to See

                                                              ii.      Light – Form of Electromagnetic Radiation that travels as a wave at the Speed of Light.

                                                            iii.      Amplitude – Affects perception of brightness (Height).

                                                            iv.      Wavelength – Affects perception of Color (Distance between Peaks).

2. The Eye

                                                               i.      Two Purposes: Channel light to the Neural Tissue that receives it (Retina). And they House the Retina.

                                                              ii.      Lens – Transparent eye Structure that focuses the light rays falling on the Retina.

                                                            iii.      Nearsightedness – Caused by Retina, Close objects are seen clearly, but distant objects appear blurry.

                                                            iv.      Farsightedness – Distant objects are seen clearly, but close objects appear blurry.

                                                             v.      Pupil – The opening into the center of the Iris that permits light to pass into the rear chamber of the eye.

                                                            vi.      Iris – Regulates the amount of Light entering the Pupil by controlling the size of the Pupil.

3. The Retina

                                                               i.      Retina – Neural Tissue lining the inside back surface of the eye; it absorbs light, processes images, and sends visual information to the brain.

1.        The Retina is a part of the Central Nervous System.

                                                              ii.      Optic Disk – A hole in the Retina where the Optic Nerve Fibers exit the eye.

4. Visual Receptors: Rods & Cones

                                                               i.      Rods Outnumber Cones.

                                                              ii.      Located in the Retina.

                                                            iii.      Cones – Play a key role in Daylight Vision and Color Vision.

                                                            iv.      Fovea – Tiny spot in the center of the Retina that contains only Cones; visual clarity is best here.

                                                             v.      Rods – Play a key role in Night Vision and Peripheral Vision.

1.        When you want to see an object in the dark, look slightly above or below where it should be to find it easier.

5. Dark and Light Adaptation

                                                               i.      Dark Adaptation – The process in which the eye becomes more sensitive to light in low illumination.

                                                              ii.      Light Adaptation – Process in which the eye becomes less sensitive to light in High Illumination.

6. Information Processing in the Retina

                                                               i.      Receptive Field of a Visual Cell – The Retina area that when stimulated, affects the firing of that Cell.

1.        Light in the Center of the Receptive Field Increases firing Rate.

2.        Light in the Outside of the Receptive Field Decreases Firing Rate.

                                                              ii.      Lateral Antagonism – Occurs when Neural Activity in a cell opposes activity in surrounding cells.

1.        Allows viewing Contrast in sight. From light falling on center or outside of Receptive Field.

7. Vision & The Brain

                                                               i.      Imaging is processed in the Brain.

                                                              ii.      Visual Pathways to the Brain

1.        Optic Chiasm – The point at which the optic Nerves from the Inside half of each eye cross over and then project to the opposite half of the Brain.

a.        Leads to Thalamus 90% of the Time. Then to Occipital Lobe.

b.       10% Leads to the Superior Colliculus, Then Thalamus, then Occipital Lobe.

                                                                                                                                       i.      Belongs to the perception of Motion and Coordination of Visual input with other Sensory Input.

c.        Main Visual Pathway leads to Magnocellular and Parvocellular channels.

d.       Parallel Processing – 2 Channels simultaneously extract different kinds of Information from the same input.

8. Information Processing in the Visual Cortex

                                                               i.      Hubel & Wiesel

1.        Feature Detectors – Neurons that respond selectively to very specific Features of more Complex Stimuli.

a.        Gets more specific as Moving along the Visual Processing System.

5. Viewing the World in Color
   
   1. Color is viewed by Wavelength (Hue) Amplitude (Brightness) and Purity (Saturation).
   2. Subtractive Color Mixing – Works by removing some Wavelength of light, leaving less light than originally there.
   3. Additive Color Mixing – Works by Superimposing Lights, putting more light in the mixture than exists in any one light by itself.
   4. Trichromatic Theory - Color Vision holds that the Human eye has 3 types of Receptors with differing sensitivities to different light wavelengths.
   5. Color Blindness – Inability to distinguish variety among colors.
   6. Complementary Colors – Pairs of Colors that produce gray tones when mixed together.
   7. Afterimage – A visual image that persists after a stimulus is removed.
   8. Opponent Process Theory – Ewald Hering – Color Vision holds that color perception depends on receptors that make antagonistic responses to three pairs of colors.
   9. Recent Studies show both Theories are somewhat Right.

                                                               i.      There are 3 Different Types of Cones

6. Perceiving Forms, Patterns, and Objects.
   
   1. Reversible Figure – A drawing that is compatible with two interpretations that can shift back and forth.
   2. The Same Visual Input can result in radically Different Perceptions.
   3. Perceptual Set – A readiness to perceive a stimulus in a particular way.
   4. Inattentional Blindness – Involves ones failure to see visible objects or events because one’s attention is focused elsewhere.

                                                               i.      Ex. You are focused on something and fail to notice another event.

5. Feature Analysis – Process of detecting specific elements in visual input and assembling them into a more complex form.

                                                               i.      You use Lines, Curves, and Corners to create and identify Objects.

6. Bottom-Up Processing – A Progression from individual elements to the whole.
7. Top-Down Processing – A progression from the Whole to the Elements.
8. Subjective Contours – Perception of Contours (Outlines) where actually none exist.
9. Both Bottom-Up and Top-Down Processing have their effect in Perception.
10. Gestalt Psychology – Influential School of Thought that emerged in Germany in 1950’s.
11. The Whole is greater than the Parts.
12. Top-Down Processing Principle.
13. Phi Phenomenon – The illusion of Movement created by presenting visual Stimuli in Rapid Succession.
14. Gestalt Principles – How the Visual System Organizes a Scene into discreet forms.

                                                               i.      Figure and Ground –

1.        Figure = Object being Looked at.

a.        Has More Substance, appear Closer, and Stand Out.

2.        Ground = Background.

                                                              ii.      Proximity – Elements that are close to one another are grouped together.

                                                            iii.      Closure – Viewers Supply Missing Elements to close or complete a Familiar figure.

                                                            iv.      Similarity – Elements that are similar are grouped together.

                                                             v.      Simplicity – Viewers Organize elements in the simplest way Possible.

                                                            vi.      Continuity – Viewers see elements in ways that produce smooth Continuation.

15. Perceptual Hypothesis

                                                               i.      Distal Stimuli – Stimuli that lies in the Distance.

                                                              ii.      Proximal Stimuli – The Stimulus energies that impinge directly on Sensory Receptors.

                                                            iii.      Perceptual Hypothesis – An inference about which distal stimuli could be responsible for the proximal stimuli sensed.

                                                            iv.      Our Perceptual Hypotheses are guided by our Experience-Based Expectations.

7. Perceiving Depth or Distance
   
   1. Depth Perception – Interpretation of Visual Cues that indicate how near or Far away Objects are.
   2. Binocular Depth Cues – Clues about Distance based on the differing views of the two eyes.
   3. Retinal Disparity – Refers to the fact that objects within 25 feet project images to slightly different locations on the Right and Left Retinas, so each eye sees a slightly Different view of the Object.
   4. Convergence – Involves sensing the eyes converging toward each other as they focus on Closer Objects.
   5. Monocular Depth Cues – Clues about the distance based on the image in either eye alone.
   6. Motion Parallax – Images at different distances move across the Retina at different Rates.
   7. Pictorial Depth Cues – Cues about distance that can be given in a flat Picture.
8. Perceiving Geographical Slant
   
   1. Hills Look even steeper when people are tired.
9. Perceptual Consistencies in Vision
   
   1. Perceptual Consistency – A tendency to experience a stable perception in the face of Continually Changing Sensory Input.
10. Visual Illusions
    
    1. Visual Illusion – An inexplicable discrepancy between the appearance of a visual Stimulus and its Physical Reality.
    2. Impossible Figures – Objects that can be represented in two-dimensional pictures but cannot exist in 3D space.
11. Hearing
    
    1. Wavelengths of Sound are measured in Frequency, or Hertz (Hz).
    2. You Selectively Hear just like you Selectively See.
    3. Amplitude is how loud the Sound is, Measured in Decibels (Db)

                                                               i.      Perceived loudness doubles every 10 Db.

4. Sensory Processing in the Ear

                                                               i.      External Ear depends upon the Vibration of Air Molecules.

                                                              ii.      Middle Ear depends upon the Vibration of Movable Bones.

                                                            iii.      Inner Ear depends upon Waves in a Fluid.

1.        This is then converted into Neural Impulses sent to the Brain.

                                                            iv.      External Ear

1.        Pinna – Sound Collecting Cone.

2.        Eardrum – Membrane that Vibrates in Response to Sound.

                                                             v.      Middle Ear

1.        Ossicles – 3 Bones that Transmit changes in Air Pressure.

                                                            vi.      Inner Ear

1.        Cochlea – Fluid Filled, Coiled tunnel that contains the Receptors for Hearing.

2.        Basilar Membrane – Runs the Length of the Spiraled Cochlea, and holds the Auditory Receptors.

12. Theories of Hearing
    
    1. Place Theory – Perception of Pitch corresponds to the Vibration of different places along the Basilar Membrane.
    2. Frequency Theory – Perception of Pitch corresponds to the rate/frequency at which the entire Basilar Membrane Vibrates.
    3. Both Theories are somewhat correct.
    4. Volley Principle – Groups of Auditory Nerve Fibers fire Neural Impulses in rapid succession, creating Volleys of Impulses.
13. Perceiving Sources of Sound
    
    1. Auditory Localization – Locating the source of a sound in Space.
    2. Loudness & Timing of Sounds are most important for finding the Source of Sound.

 

14. Taste and Smell
    
    1. Gustatory System – The Sensory system for Taste.
    2. Olfactory System – The Sensory system for Smell.
    3. Odor of Food greatly adds to Flavor of Food.
    4. Taste Buds – Receptive for Taste in the Mouth.
    5. Cilia – Receptive for Smell in the Nose.
15. Touch
    
    1. Receptive Field for Touch – When touched Neurons fire to the Brain alerting it.
    2. Pain – Slow and Fast Pathways to the Brain.
    3. Pain is a response that is subjective in the Brain.
    4. Gate-Control Theory – Incoming Pain Sensations must pass through a “gate” in the Spinal Cord that can be closed, thus blocking ascending Pain Signals.
    5. Endorphins can dull Pain.
16. Other Senses
    
    1. Kinesthetic System – Monitors the Positions of the Various parts of the Body.
    2. Vestibular System – Responds to Gravity and keeps you informed of your body’s location in Space.

                                                               i.      Provides sense of Balance.